Video encoding and decoding method, video encoder, and video decoder

Abstract

A video decoding method according to the present disclosure includes the steps of: determining whether a merge motion difference coding method is applied to a current block; generating a merge candidate list for the current block; specifying a merge candidate for the current block based on the merge candidate list; and deriving a motion vector for the current block based on the merge candidate.

What is claimed is: 
     
         1 . A video decoding method comprising:
 determining whether a merge motion difference coding method is applied to a current block;   generating a merge candidate list for the current block;   specifying a merge candidate for the current block based on the merge candidate list; and   deriving a motion vector for the current block based on the merge candidate, wherein   when the merge motion difference coding method is applied to the current block, the motion vector of the current block is derived by adding an offset vector to a motion vector of the merge candidate,   when a maximum number of merge candidates that the merge candidate list may include is plural, the merge candidate of the current block is selected based on index information decoded from a bitstream indicating any one among the merge candidates, and   when the maximum number is 1, the merge candidate is determined without decoding the index information.   
     
     
         2 . The method according to  claim 1 , wherein a magnitude of the offset vector is determined based on first index information specifying one among motion magnitude candidates. 
     
     
         3 . The method according to  claim 2 , wherein at least one among a maximum value and a minimum value of the motion magnitude candidates is set differently according to a value of a flag indicating numerical values of the motion magnitude candidates, wherein the flag is signaled at a picture level. 
     
     
         4 . The method according to  claim 2 , wherein at least one among a maximum value and a minimum value of the motion magnitude candidates is set differently according to motion vector precision for the current block. 
     
     
         5 . The method according to  claim 2 , wherein a direction of the offset vector is determined based on second index information specifying one among vector direction candidates. 
     
     
         6 . A video encoding method comprising:
 determining whether a merge motion difference coding method is applied to a current block;   generating a merge candidate list for the current block;   specifying a merge candidate for the current block based on the merge candidate list; and   deriving a motion vector for the current block based on the merge candidate, wherein   when the merge motion difference coding method is applied to the current block, the motion vector of the current block is derived by adding an offset vector to a motion vector of the merge candidate,   when a maximum number of merge candidates that the merge candidate list may include is plural, index information indicating the merge candidate of the current block among the merge candidates is encoded, and   when the maximum number is 1, encoding of the index information is omitted.   
     
     
         7 . The method according to  claim 6 , further comprising the step of encoding first index information for specifying a motion magnitude candidate indicating a magnitude of the offset vector among a plurality of motion magnitude candidates. 
     
     
         8 . The method according to  claim 7 , further comprising the step of encoding a flag indicating numerical values of the motion magnitude candidates, wherein at least one among a maximum value and a minimum value of the motion magnitude candidates is set differently according to a value of the flag, and wherein the flag is encoded at a picture level. 
     
     
         9 . The method according to  claim 7 , wherein at least one among a maximum value and a minimum value of the motion magnitude candidates is set differently according to motion vector precision for the current block. 
     
     
         10 . The method according to  claim 7 , further comprising the step of encoding second index information for specifying a vector direction candidate indicating a direction of the offset vector among a plurality of vector direction candidates. 
     
     
         11 . A video decoder comprising:
 at least one processor; and   a memory storing computer programs which, when executed by the at least one processor, cause the at least one processor to:   determine whether a merge motion difference coding method is applied to a current block;   generate a merge candidate list for the current block;   specify a merge candidate for the current block based on the merge candidate list; and   derive a motion vector for the current block based on the merge candidate, wherein   when the merge motion difference coding method is applied to the current block, the motion vector of the current block is derived by adding an offset vector to a motion vector of the merge candidate,   when a maximum number of merge candidates that the merge candidate list may include is plural, the merge candidate of the current block is selected based on index information decoded from a bitstream indicating any one among the merge candidates, and   when the maximum number is 1, the merge candidate is determined without decoding the index information.   
     
     
         12 . The video decoder according to  claim 11 , wherein a magnitude of the offset vector is determined based on first index information specifying one among motion magnitude candidates. 
     
     
         13 . The video decoder according to  claim 12 , wherein at least one among a maximum value and a minimum value of the motion magnitude candidates is set differently according to a value of a flag indicating numerical values of the motion magnitude candidates, wherein the flag is signaled at a picture level. 
     
     
         14 . The video decoder according to  claim 12 , wherein at least one among a maximum value and a minimum value of the motion magnitude candidates is set differently according to motion vector precision for the current block. 
     
     
         15 . The video decoder according to  claim 12 , wherein a direction of the offset vector is determined based on second index information specifying one among vector direction candidates. 
     
     
         16 . A video encoder comprising:
 at least one processor; and   a memory storing computer programs which, when executed by the at least one processor, cause the at least one processor to:   determine whether a merge motion difference coding method is applied to a current block;   generate a merge candidate list for the current block;   specify a merge candidate for the current block based on the merge candidate list; and   derive a motion vector for the current block based on the merge candidate, wherein   when the merge motion difference coding method is applied to the current block, the motion vector of the current block is derived by adding an offset vector to a motion vector of the merge candidate,   when a maximum number of merge candidates that the merge candidate list may include is plural, index information indicating the merge candidate of the current block among the merge candidates is encoded, and   when the maximum number is 1, encoding of the index information is omitted.   
     
     
         17 . The video encoder according to  claim 16 , wherein the computer programs, when executed by the at least one processor, further cause the at least one processor to:
 encode first index information for specifying a motion magnitude candidate indicating a magnitude of the offset vector among a plurality of motion magnitude candidates.   
     
     
         18 . The video encoder according to  claim 17 , wherein the computer programs, when executed by the at least one processor, further cause the at least one processor to:
 encode a flag indicating numerical values of the motion magnitude candidates, wherein at least one among a maximum value and a minimum value of the motion magnitude candidates is set differently according to a value of the flag, and wherein the flag is encoded at a picture level.   
     
     
         19 . The video encoder according to  claim 17 , wherein at least one among a maximum value and a minimum value of the motion magnitude candidates is set differently according to motion vector precision for the current block. 
     
     
         20 . The video encoder according to  claim 17 , wherein the computer programs, when executed by the at least one processor, further cause the at least one processor to:
 encode second index information for specifying a vector direction candidate indicating a direction of the offset vector among a plurality of vector direction candidates.